Wood treatment and product



Patented Dec. 1, 1936 UNETED STATES WOOD TREATNIENT AND PRODUCT Joseph L. Goodale, Ipswich, Mass.

No Drawing. Application March 15, 1935, Serial No. 11,317

8 Claims.

The present invention relates to the treatment of wood to protect the same against attack by marine borers, termites and the like, and to the product of such treatment.

The destructive attacks of marine borers and termites upon wood piling, posts, and in fact any wood to which they have access, is a source of great loss. It is an object of the present invention to provide an improved treatment which will protect the wood against attack by these organisms and also a novel product comprising wood so treated.

In general, my improved treatment of the Wood involves the introduction of a colloidal arsenic compound, for example, a colloidal dispersion of arsenic sulfide or sulfides, preferably stabilized by a protective colloid, and eventual precipitation of the suspensoid and emulsoid in the wood. The selection of a protective colloid such as gelatin or glue, which is afiected by tannin, is advantageous in that while such protective colloid will act to maintain the arsenic sulfides in a colloidal condition during impregnation of the wood, the tannin generally present in wood will then act upon the gelatin to cause or permit agglomeration of the colloidal particles and the arsenic sulfides will be deposited in the intercellular spaces (often referred to in the art as air cavities or air cells) of the wood. The use of a protective colloid which is coagulated by tannin already present in the wood also results in occlusion of the air cavities of the wood by the coagulated gelatin and consequently diminishes the extent to which the toxic deposit is exposed to leaching.

The toxic efiect of the arsenic so deposited protects the wood against the attack of destructive animal organisms. Although arsenic sulfides are practically insoluble in water and thus resist leaching from the wood, in the digestive tract of an animal organism they give the characteristic arsenic action on the organism.

The colloidal dispersion of arsenic sulfide is conveniently prepared by adding a soluble sulfide to a soluble salt of arsenious acid in the presence of a protective co1loid,preierably a protective colloid coagulable by tannin. It is believed that arsenious trisulfide and other sulfides of arsenic may be formed.

As an example of one method of preparing a colloidal dispersion of arsenic sulfide for use in my invention I give the following: A 1% aqueous solution of sodium arsem'te in which is dissolved one to ten grams of gelatin per liter of solution is mixed with about one-half its volume or more of calcium persulfide solution having a specific gravity of 1.010. Sodium arsenite, gelatin and calcium persulfide are inexpensive and readily handled materials well adapted for use in preparing the colloid but it will be obvious that 5 other materials and procedures are available and fall within the scope of my invention.

The colloidal dispersion may be introduced into the Wood (preferably to refusal) by standard commercial processes, such, for example, as the 1 standard vacuum pressure process or any other suitable process. The presence of the protective colloid maintains the sulfide particles in a state of dispersion during the time necessary for introduction into the wood. After such introduc- 15 tion these particles gather together in clusters which are too large to be translocated from their position in the intercellular spaces of the wood. If the wood contains tannin, the tannin causes coagulation of the gelatine, which becomes insoluble and elastic. The physical structure of the wood should be sufiiciently porous to permit adequate penetration of the colloid.

I do not use the term arsenic herein to designate any particular valence of this element, 25 but broadly to designate any valence thereof.

As a result of my treatment, toxic arsenic sulfides are deposited within the wood and protect the wood against attack by destructive organ isms as previously mentioned.

I claim:

1. The method of treating wood which comprises introducing a colloidal dispersion of arsenic sulfide in the presence of a protective colloid into the wood, the tannin in the wood act- 35 ing upon the protective colloid to cause agglomeration of the colloidal particles whereby arsenic sulfide is deposited in intercellular spaces of the wood.

2. The method which comprises introducing 4o colloidal arsenic sulfide in the form of a sol containing gelatin, into intercellular spaces of wood, the gelatin acting to preserve the colloidal state of the arsenic sulfide during introduction but the action of a constituent in the wood then 45 causing the colloidal arsenic sulfide particles to agglomerate, whereby arsenic sulfide is deposited within the wood.

3. The treatment of wood which comprises as steps mixing a soluble salt of arsenious acid, in 50 the presence of a protective colloid, with a soluble sulfide to produce colloidal arsenic sulfide, impregnating wood with the resulting sol, agglomerating the colloidal particles and depositing arsenic sulfide in the Wood.

4. The method of treating wood which comprises mixing a solution of sodium arsenite containing gelatin with a solution of calcium persulfide to form colloidal arsenic trisulfide, introducing the resulting arsenic sulfide into intercellular spaces of the Wood and coagulating the colloidal particles to deposit arsenic sulfide in the intercellular spaces of the wood.

5 The method which comprises introducing into wood colloidal arsenic sulfide, said sulfide being in. the form of a sol containing gelatin, whereupon tannin in the wood acts upon the gelatin to cause agglomeration of the colloidal particles and arsenic and water-insoluble gelatin are deposited within the wood.

6. The method of treating wood which comprises introducing colloidal arsenic sulfide, in

the presence of a protective colloid, into the wood, whereupon a constituent of the wood acts to agglomerate the colloidal arsenic sulfide particles, whereby arsenic sulfide is deposited in intercellular spaces of the wood.

7. As a new product, wood containing a coagulated sol of arsenic sulfide, said arsenic sulfide being present as a deposit in the wood after action by a constituent of the wood on a colloidal dispersion of arsenic sulfide containing a protective colloid.

8. As a new product, wood impregnated with a coagulated sol of arsenic sulfide and a protective colloid comprising gelatin, said arsenic sulfide being present as a deposit, after action on said gelatin by a constituent of the wood.

JOSEPH L. GOODALE. 

